Charter flights to bring in agricultural workers from eastern Europe are needed as a matter of urgency, otherwise fruit and vegetables will be left unpicked in Britain’s fields, the government is being warned.

Some large farms have already been chartering planes to bring in labour from eastern Europe. But farming organisations and recruitment agencies say that, in the face of massive disruption to the agricultural sector caused by the spread of the coronavirus, the government needs to step in and help organise more flights.

Some 90,000 positions need to be filled, many in just a few weeks’ time. One leading supplier, the charity Concordia, was looking to bring in around 10,000 labourers – half from the EU and the rest from Russia, Moldova, Ukraine, Belarus, Georgia and Barbados. But all of the non-EU countries are closed. On Wednesday, in a big setback, Ukraine extended its lockdown from 2 April until 23 April.

Stephanie Maurel, Concordia’s chief executive, said: “Our recruitment outside the EU is stalled which leaves us with Lithuania, which has closed borders, Romania with no airplanes, and Bulgaria which is our little beacon.”

Although Bulgaria is on countrywide lockdown, farm workers are classed as key workers and can move around the country. But most airlines that operate in Bulgaria – including EasyJet – are grounded. A Wizz Air flight bringing in 450 people landed a week ago on Saturday.

“We’re talking about chartering planes to bring workers in,” Maurel said. “It costs around £10,000 for an hour’s flight carrying 229 people – that’s €45,000 Sofia to London, or around €250 per person.”

Maurel, who said the plan was being actively discussed by both the National Farmers’ Union and the Association of Labour Providers, called on the government to help provide urgent clarity.

“If I put up reserves and guarantees [to secure a charter flight], I need to know it can take off.”

Some farms were struggling even before the crisis hit. A tightening of the labour market, a combination of Brexit and the booming domestic economies of eastern Europe proving more attractive to seasonal workers, had seen a decline in the number of fruit and vegetable pickers coming to the UK.

“Because of the tightening of labour, we had already lost a percentage of farms,” Maurel said. “This will finish others off. You won’t have fruit and veg in shops. Asparagus and beans start in a couple of weeks, cucumbers early April, tomatoes are all year round; in May it’s soft fruits – strawberries, raspberries; lettuces have been in the ground since December.”

Nick Marston, the chairman of British Summer Fruits, which represents soft fruit growers, acknowledged that his industry was “entering an unprecedented time”.

Last year, 98% of fruit pickers – now classed as “key workers” – came from outside the UK, the vast majority from Bulgaria and Romania.

British growers have been contacting companies in the hospitality sector to recruit laid-off staff.

“We are very optimistic about the ability of UK residents to come out and help us,” Marston said. “They may be people from eastern Europe who were working here in the hospitality sector, who are relatively young and don’t have that many ties and want a job paying reasonable pay in reasonable conditions.”

The environment secretary, George Eustice said: “Our farmers are doing a fantastic job of feeding the nation during this immensely challenging time. I have been speaking with industry about the critically important issue of seasonal workers, who usually come from Europe to pick fruit and vegetables.

“We need to mobilise the British workforce to fill that gap and make sure our excellent fruit and vegetables are on people’s plates over the summer months. There are already brilliant recruitment efforts underway by industry and I would encourage as many people as possible to sign up.

“We will also be looking at other ways to make sure farmers have support they need ahead of the busy harvest months, while also keeping workers safe and protected.”